Elastic bearing with hydraulic damping properties

ABSTRACT

A pneumatically regulated elastic bearing dampens hydraulically and decouples vibrations of a small amplitude using a freely displaceable element. The bearing can be engaged using a pneumatically activated control chamber, which has a miniature configuration and is located beneath the freely displaceable element, in such a way that the element forms a deformable or displaceable wall for the control chamber. In place of a compensation regulation, in the control chamber, a shift to one of three possible pneumatically determined control states preferably takes place. The states are VENTILATED, CLOSED and PRESSURIZED.

[0001] The present invention relates to a hydraulically damped elasticbearing according to the preamble of claim 1.

[0002] Such bearings comprising a loose piece for uncoupling vibrationsare commonly known in the state of the art for numerous disclosures ofdifferent embodiments. A loose piece in such a bearing may be a disc orannular disc. In fact it is disposed loosely in a cavity or adisc-shaped material configured in a different manner which isvibratory, especially vibratory in axial direction with respect to itsmain surfaces, and which is restrained in a safety device, namely aso-called cavity, enclosing the loose piece with a clearance. Instead ofusing a piece of metal or rubber which is unfixed and therefore looselyinserted in the cavity it is also common to use an elastomer diaphragmas a loose piece. Such a diaphragm is thin, also partly reinforced andvibratory. However, according to the state of the art said loose piecesare disposed in cavities of the aforementioned kind to limit thevibration of such uncoupling diaphragms to a certain deformation pathcorresponding to the low amplitudes of the vibrations to be uncoupledand the path-length thereof. Accordingly, the term “loose piece” used inthe following comprises, besides uncoupling elements being unfixed inpath-way limiting cavities, also uncoupling diaphragms of theaforementioned kind.

[0003] Furthermore, in the field of automotive engineering numerousmeans to expand the field of use and to improve the comfort ofuncoupling or not uncoupling hydraulic bearings are known, which actupon the damping fluid and change the bearing characteristics thereby.Said means are, however, mostly devices which affect the damping fluidby means of rheological, hydraulical, configurative vibrational,mechanical or pneumatical regulation and compensation forces.

[0004] In this context propositions have been known for a long time tochange the characteristics of hydraulic bearings during their use, i.e.during the dynamical loading of the hydraulic bearing, in a moreeffective way by damping or absorbing unwanted vibration introduced intothe bearing by means of pneumatic compensation. In recent years this hasall the way been accomplished by pneumatically acting on the outer sideof a compensation diaphragm bounding a compensation chamber. Thediaphragm normally does not influence the damping performance, and thecharacteristics of a hydraulic bearing. Thus, contrary to its originaldestination as a spring, the compensating diaphragm is remodelled to acomponent of the bearing significantly modifying the bearingcharacteristics. In case of unwanted high amplitude vibrations forexample it stiffens the spring and in case of unwanted low amplitudevibrations it flattens the spring characteristic curve. This pneumaticaleffect can be realized by means of compression as known for example fromDE 32 10 731 A1, however, it is also possible to use a depressionregulation as disclosed in EP 851 146 A1.

[0005] Commonly known pneumatically controllable hydraulic bearings are,however, luxury articles regardless of their functional capability. Theyrequire complicated real time controlling systems. Additionally, inorder to generate the required forces for the compensation diaphragmwith its relatively large surface area pneumatic compressors, buffertanks and switching systems are needed which are dimensioned in a waythat these means have to be located outside the hydraulic bearing to becontrolled since it is not possible to integrate them in the limitedspace of such bearings.

[0006] Starting from the state of the art described above it is anobject of the invention to provide a hydraulic bearing especially anpower unit bearing for automotive engineering which is practical withrespect to its size, cost and power, which allows for a reducedpneumatic expense and which provides a spring characteristic which canbe influenced effectively.

[0007] The invention solves this problem by an elastic bearing providingthe features of claim 1.

[0008] It is an essential feature of the invention that the pneumaticswitching of a hydraulic bearing which is constructed in a classical wayis not achieved by acting on the compensating diaphragm but by acting onthe uncoupling element especially on an uncoupling diaphragm, namely aloose piece. This allows for a reduction and minimization of therequired pneumatical expense especially with respect to the requiredsize of the pneumatic component.

[0009] According to an embodiment this basic idea of the invention isfurther developed and instead of using a compensation control much moresimple and practical means are provided replacing the control by anadjustable setting of three different operation states of the bearing inorder to set the dampening function of the hydraulic bearing to SMOOTH,MEDIUM-HARD and HARD. It is in general sufficient that the threeadjustable dampening states are predetermined by the driver at theconsole of an automobile. in case the automobile is equipped with asensor technology the three states of the hydraulic bearing according tothe invention can be switched pneumatically as a result of a read outprocess of the controller of the automobile. When air is used as aswitching medium three dampening states are provided which have aninherent band width and a dynamic to make a real time compensation andits complicated controlling technique needless, even in a conceptionalview.

[0010] Further embodiments of the invention are objects of the dependentclaims.

[0011] The invention is elucidated below by means of illustrativeembodiments and in relation to the drawings.

[0012]FIG. 1 shows a first embodiment of a hydraulic bearing accordingto the invention in axial section.

[0013]FIG. 2 shows a second embodiment of a hydraulic bearing accordingto the invention and

[0014]FIG. 3 shows a block diagram of the components of the pneumatichydraulic bearing according to the invention.

[0015] A first embodiment of the hydraulic bearing according to theinvention is shown in FIG. 1 in axial section. The power unit bearingpresented here is designed for use in an motor vehicle. The bearingessentially comprises a conical annular support spring 1 supporting aload connection fitting 2 carrying a threaded connection bold 3 forconnecting the power unit. The support spring 1 rests indirectly on acup-shaped chassis connection fitting 4. A common separating disc isinserted between the load connection fitting 4 and the chassis-side edgeof the support spring 1. A working chamber filled with hydraulic dampingfluid is defined between the separating disc 5 and the support spring 1.This working chamber 6 is usually connected with a compensating chamber8 through a throttle channel 7 which is part of the separating disc. Thecompensating chamber 8 is formed in a pressure-proof and fluid-tightmanner between the chassis-side surface of separating disc 5 and acompensating diaphragm 9. Said diaphragm 9 is elastically andessentially resistanceless deformable. In case of a deformation of thesupport spring 1 the hydraulic damping fluid is pumped from the workingchamber 6 through the throttle channel 7 into the compensating chamber 8and the compensating diaphragm is deformed resistanceless into the emptyspace 10 which is provided in the cup-shaped chassis connection fitting4.

[0016] An annular cavity 11 is fixedly clamped between the chassis-sideedge of the support spring 1 and the load-side surface of the separatingdisc 7. This cavity essentially consists of a peripheral annular portionextending around the circumference and clamping the cavity. Said portionprovides star-shaped joints 12 supporting a central annular anddome-like portion which is the real loose cavity 13. The loose cavity isfixedly clamped in a pressure-proof and fluid-tight manner at itschassis-side annular rim to the outer periphery of a rolling ply 14.This defines an uncoupling chamber 16 between an elastomer loose piece15 supported in central position of the rolling ply and the loose cavity13. The loose cavity 13 hydraulically communicates with the dampingfluid of the operational chamber 6 by means of passages 17. The loosepiece and the annular rolling ply are positioned in a central recess 18provided in the separating disc 5.

[0017] As shown in FIG. 1 the chassis-side surface of the loose cavity13 which is configured in a dome-type manner and the surface of theloose piece 15 facing that surface are dimensioned and configuredcomplementary to each other. Thus, the passages connecting theuncoupling chamber 16 and the damping fluid of the working chamber 6 canbe closed in a fluid-tight and pressure-proof manner by lifting andpressing the loose piece 15 in and against the dome of the loose cavity13.

[0018] Furthermore, the central recess 18 in the separating disc 5 isconfigured in a cup-shaped manner defining a controlling chamber 19between the chassis-side lower surface of the loose piece 19 and therolling ply 14. The loose piece is movable in axial direction due to itsrolling ply. It can be moved into and out of the controlling chamber 19.This axial movement is either a vibrational movement under the influenceof vibrations introduced by the damping fluid or a movement caused bypneumatic pressure which can be generated in the controlling chamber 19by means of a pneumatic device 21 which is connected by a pneumaticconnection 20. As shown in FIG. 1 the pneumatic device is not onlyintegrated in the bearing especially in the cup-shaped chassisconnection fitting 4 but provides the necessary expanding space 10required by the compensating diaphragm 9 which is connected with anouter ventilation.

[0019] A bearing constructed in this way is clamped in an annular casing22. In FIG. 1 the chassis-side rim 23 of the casing 22 of the bearing isshown in a pre-assembled state of the bearing. After the final assemblyof the hydraulic bearing the chassis-side rim 23 of the casing 22 isradially crimped inwards under an outer flange 2 which is formed on thechassis connection fitting 4.

[0020] In FIG. 3 the pneumatic device 22 is shown in more detail as ablock diagram.

[0021] According to FIG. 3 the pneumatic device 21 consists of twoparts, namely a compressor having an intake fitting 26 and a pressurefitting 27 which is connected with a {fraction (3/2)}-port directionalcontrol valve 29 through a conduct 28. An outlet fitting 30 is connectedwith the fitting 20 of the controlling chamber 19 by connection 21comprising a movable partition, namely the loose piece 15 supported bythe rolling ply 18. The uncoupling chamber 16 has been described indetail in connection with the embodiment according to FIG. 1. It isschematically outlined lying opposite the controlling chamber 19.

[0022] The {fraction (3/2)}-port directional control valve is designedto provide three switching states at its outlet 30. These states areOPEN, CLOSED and PRESSURIZED. In the schematical block diagram of FIG. 3the {fraction (3/2)}-port directional control valve 29 is shown in theOPEN state.

[0023] In said OPEN state the valve fitting 30 freely communicates withthe ambient atmosphere. Thus, the valve is open and the compressor 25 isswitched to an inoperative state. Appropriately, the compressor is

[0024] In said OPEN state the valve fitting 30 freely communicates withthe ambient atmosphere. Thus, the valve is open and the compressor 25 isswitched to an inoperative state. Appropriately, the compressor isswitched off. Thus, the controlling chamber 19 is set under atmosphericpressure at least as long as the loose piece 15 is freely displaceable.

[0025] In the CLOSED state the pump is still inoperative. However, theconnection with the atmosphere is closed. The air volume in thecontrolling chamber is closed off. Accordingly the vibration of theloose piece 15 in the controlling chamber generates a low underpressureor a low overpressure according to the phase of the vibration. Thisinfluences in a controlling manner the movability of the loose piece andaccordingly the characteristic of the whole hydraulic bearing as beingstiffened in a moderate way.

[0026] Finally in the PRESSURIZED state the compressor 25 is inoperation, i.e. switched on, and connected with the {fraction(3/2)}-port directional control valve by a conduct 28. This valveconnection communicates with an outlet 30. The passage to the atmosphererests closed.

[0027] In this switching state the controlling chamber 19 ispneumatically set under overpressure delivered by the compressor 25.Alternatively, it is set under an offset pressure which is regulated bya valve by using the overpressure delivered by the compressor as apreset value. For pneumatically switching of usual power unit bearingsfor motor vehicles this static offset pressure is of about a hundreds ofmillibars especially about five hundred millibars. Under thesecircumstances the movability of the uncoupling loose piece is furtherhindered or restricted essentially stiffening once again the hydraulicbearing as a whole with respect to the switching state CLOSED.

[0028] By use of a simple compressor 25 and a simple {fraction(3/2)}-port directional control valve 29 pneumatically acting upon anuncoupling loose piece 15 of states can be realized without high costsand even for low-prize motor vehicles which are produced in series oflow run. In practice this setting of three defined states of the springis more pleasant for the driver compared to an expensive, complicatedand less effective real-time regulation of pneumatic or hydraulic kind.

[0029] In principle the switching from one of the present switchingstates of the hydraulic bearing into another can be performed at theinstrument panel of the motor vehicle so that the driver can adjust theperformance and road behaviour of the vehicle according to what hepersonally considers appropriate or comfortable. However, saidadjustment can also be performed automatically by an equipment onboard—which nowadays is common even in the most simple vehicles—forexample by using the engine speed as a set value.

[0030] In FIG. 2 a second embodiment of a hydraulic bearing withfeatures according to the invention is shown in parts. In contrast tothe bearing shown in FIG. 1 in FIG. 2 the loose piece 215 is notassigned as a central disc but as an annular disc formed in an annularloose cavity 216. Accordingly the loose piece is not linked with anannular rolling ply which extends around the circumference. It is linkedwith a rolling ply 214′ radially located inside and with a rolling ply214 radially located outside. Furthermore, according to FIG. 2, thecup-shaped cylindrical controlling chamber 19 is configured in form ofan annular controlling chamber 219. In contrast to the pneumatic device21 being integrated in the hydraulic bearing, as illustrated in FIG. 1,the pneumatic device according to FIG. 2 is located outside the innerspace of the hydraulic bearing. This is not shown in FIG. 2.Accordingly, the pneumatic device is completely separated from thehydraulic bearing or externally mounted. When a conduct 220 is used thecontrolling chamber 219 of the embodiment shown in FIG. 2 is alsoswitchable to one of the three states OPEN, CLOSED and PRESSURIZEDdescribed above basically in the same way as described in connectionwith the embodiment according to FIG. 1. Finally, the embodiment of ahydraulic bearing shown in FIG. 2 by illustrating its essential elementswhich comprise the features according to the invention this embodimentis also characterized by a chassis connection fitting 204 which is notfixed to the chassis by a threaded bold 43 (FIG. 1) but by means of aflange connection fitting 243. Thus the separating disc 205 is not fixedon but directly in the chassis connection fitting 204.

[0031] The embodiment of the hydraulic bearing according to theinvention shown in FIG. 2 has the advantage of an extremely lowconstruction. Furthermore it provides at the same time a pneumaticallyadjustable hydraulic bearing.

1. Hydraulically damping elastic bearing especially power unit bearingcomprising a conical annular support spring supporting a load connectionfitting and resting directly or indirectly on a chassis connectionfitting; a separating disc; a hydraulic working chamber filled withhydraulic damping fluid and defined between the separating disc and thesupport spring; a throttling channel connecting the working chamber withan compensating chamber opposed to the working chamber and definedbetween the separating disc and an elastic easily deformablecompensating diaphragm; a loose piece for uncoupling low amplitudevibrations which is trapped in a cavity to be freely displaceable in adirection perpendicular to the plane of the separating disc; a casingenclosing the bearing and connecting the components of the bearing whichare located in axial succession in a fluid-tight and fixed manner; theloose piece (15; 215) being disc-shaped and fixed to a separating disc(5) at its outer periphery by means of rolling plies (14; 214, 214′);said loose piece being in contact with the damping fluid at its surfacefacing the working chamber and defining at its opposed surface a movablepartition of a controlling chamber (19; 219) which can be pressurizedpneumatically and which is separated from both the working chamber (6)and compensating chamber (8) characterized by the combination of acompressor with a {fraction (3/2)}-port directional control valve (29)for switching the controlling chamber (19; 219) in one of the threestates OPEN, CLOSED and PRESSURIZED.
 2. A bearing according to claim 1characterized by a loose cavity (11, 13; 213) clamping the rolling ply(14; 214, 214′) of the loose piece (15; 215) at its periphery extendingaround the circumference in a pressure-proof and fluid-tight manner anda loose piece bounding an uncoupling chamber (16; 216) whichcommunicates with the damping fluid of the working chamber throughpassages (17; 217) provided at the load-sided partition of the loosecavity.
 3. Bearing according to claim 2 characterized by an elastomerloose piece (15; 215) having a surface facing the uncoupling chamberwhich is complementary to the surface of the cavity (13; 213) facing theuncoupling chamber and which is configured in a manner that the loosepiece rests motionless against the cavity wall during the PRESSURIZEDstate sealing the uncoupling chamber (16; 216) against the workingchamber in a compression-proof and fluid-tight manner.
 4. Bearingaccording to one of the claims 1-3 characterized by a cup-shapedconfiguration of the chassis connection fitting (4) which is designedlike a bottom of a casing for integrating the compressor (25) and the{fraction (3/2)}-port directional control valve (29).